This invention relates to a method of electrochemical treatment such as electroplating, etc. and an electrochemical reaction apparatus thereof, which method and apparatus are suited to be used for electrochemical treatment such as, for example, electroplating, and the like, which method and apparatus are capable of executing various treatment processes safely, rationally and rapidly, using supercritical or subcritical matter such as, for example, carbon dioxide, which method and apparatus are capable of processing the used-carbon dioxide, treatment solution, etc. rationally and rapidly, which method and apparatus are capable of suppressing the consumption of the amount of the acid picking solution, plating solution, etc. and reducing the amount of liquid waste generated from the plating operation thereby preventing the pollution of the environment and achieving the improvement of the working environment, the enhancement of productivity and the reuse of the liquid waste, which method and apparatus are capable of attaining a beautiful finishing by remarkably improving the adhesion power of plating, which method and apparatus are capable of easily realizing fine and uniform plating even at the reverse side and recessed-portion of the matter to be treated, which method and apparatus are capable of attaining the elimination miniaturization and light-weight of a vessel(s) required for each treatment thereby achieving the reduction of the cost of equipment and the compactness of the installation space, and which method and apparatus are capable of executing electrochemical reaction rationally and efficiently by pressurizing the reaction vessel and suppressing electrolysis of a solvent in the electrolytic solution for the enhancement of electric current efficiency, thereby obtaining a fine and thin metallic film.
As a representative example of a convention electrochemical reaction, there can be listed electroplating. The electroplating plays an important role in industrial use such as decoration, corrosion prevention, corrosion resistance, rust prevention and the like. Also, as an example of a method of mass production of a specific metal, there can be listed electrorefining. Besides the above, as examples of electrochemical treatment in which application of an external electric field is employed, there can be listed electroforming, electrophoretic coating and the like, which are all in the category of cathodizing treatment, and formation of anodic oxide film of aluminum, electrochemical polishing, electrochemical machining, electrophoretic plating and the like, which are all in the category of anodizing treatment. Moreover, as examples of a method in which application of an external electric field is not employed, there can be listed electroless plating, chemical conversion treatment and the like.
Various attempts have heretofore been made in order to improve the reaction efficiency or to improve the uniformity and adhesion power of film in respect of the above-mentioned various electrochemical reaction methods.
As one example of them, a method is known in which a surface active agent is used. The surface active agent plays an important role in suppressing gas generated from electrochemical reaction, breaking water, suppressing the occurrence of stain, assisting drying and the like.
In addition, by using the surface active agent, reaction can be executed without using any auxiliary electrode even at a feeble electric current portion with high electric characteristics. Owing to this feature, the consumption of electric power can be reduced and the speed of deposition and dissolution can be increased. As a result, the leveling effect can be increased.
However, the surface active agent is actually not used because of its high price, complicated process, etc. Therefore, development of a new technique is demanded which is capable of enhancing the reactability and reaction efficiency and improving the uniformity and adhesion power of the film.
Also, in the technical field of electrochemical reaction such as electroplating, etc., there is encountered with a problem of treatment of liquid waste such as used-plating solution. This is regarded as a problem to be solved as more rapidly as possible with the increasing concern about the environment problem.
The liquid waste treatment includes three stages of process, namely, decomposition of toxic matter contained in liquid waste, separation and removal of toxic matter from the liquid waste, and treatment and disposal of the separated matter.
Especially, with respect to the separation of toxic matter from the liquid waste, a method is widely accepted, in which a chemical is applied to the liquid waste to solidify the toxic matter and then the solidified toxic matter is removed.
However, this method is, in many cases, executed using a large scaled-equipment which, in general, cannot be said very efficiency and it cannot fully cope with the problem of treatment of liquid waste under the recent increasing strict restriction by rules and regulations.
Moreover, conventionally, it was necessary to clean the target matter such as a plated electrode after electrochemical reaction. This cleaning process is normally executed by rinsing the target matter in stored water, exposing the target matter to running water or the like. Thus, it gives rise to a problem that the process becomes complicated. Moreover, the solution used for cleaning becomes a large quantity of liquid waste and this again raises the above-mentioned problem of treatment of liquid waste.
The conventional electroplating process can roughly be classified into a preceding treatment process (namely, pre-treatment process), a plating treatment process and a succeeding treatment process (namely, post-treatment process). Of these treatment processes, the preceding treatment process includes a step of degreasing and cleaning. In ordinary practice, this preceding treatment process is executed in an exclusive-use vessel containing a prescribed treatment solution, the vessel being then heated and the matter to be treated being then immersed in the treatment solution for a predetermined time.
Therefore, a plurality of vessels and work spaces for them are required which results in high cost of the equipment. Moreover, a poor working environment is created where work must be done under such circumstance that the treatment solution is scattered and hazardous gases are generated. In addition, since it takes a long time for immersing the matter to be treated in the treatment solution, productivity is lowered.
As a degreasing/cleaning method, various methods are proposed such as, alkali heating, electrocleaning, solvent cleaning, emulsion cleaning and the like. However, all of them require the use of chemicals and special equipment. Moreover, it is required for them to immerse the matter to be treated in various treatment solutions or expose the matter to be treated to evaporation of the treatment solutions. Therefore, much time is required for them to break water.
As one attempt to solve such problems, Japanese Patent Application Unexamined Publication No. 2000-63891, for example, discloses a cleaning apparatus in which carbon dioxide in a supercritical state is supplied into a chamber of small capacity and contacted with matter to be cleaned which is stored in the chamber, and then, the matter to be cleaned is heated or vibrated so that the PCB adhered to the matter to be cleaned is dissolved and removed.
In this conventional cleaning apparatus, the carbon dioxide in a critical state is all discharged to the atmospheric air after the cleaning operation is finished. Therefore, in the case where an electroplating product having a larger capacity than the above-mentioned chamber is to be cleaned, the consumption of carbon dioxide is increased, thus making the method of using this conventional apparatus expensive. Moreover, it can be expected that the working environment is deteriorated due to discharge of carbon dioxide. Thus, this conventional apparatus is difficult to be actually put into practice.
Moreover, the conventional plating process requires a plurality of water washing treatment processes which are located adjacent to the plating vessel(s) and water must be normally supplied to the main water washing vessel. This makes the equipment cost high. In addition, the consumption of water is increased.
Moreover, it is very troublesome and labor consuming to recollect the plating solution (so-called pumping back) at the time of taking the matter to be plated out of the plating vessel. In addition, since the recollected solution must be condensed, productivity is very low.
On the other hand, the conventional plating technique is generally poor in adhesion power of plating and the plating is hardly adhered to the reverse side and recessed part of the matter to be treated where electric current density is low. Therefore, when such area of the matter to be treated is the target area to be plated, change of direction must be made before the plating treatment is executed or otherwise, it is required to install a secondary electrode at such area. Accordingly, this conventional plating technique cannot cope with the requirement for plating a deformed matter.
Moreover, in the conventional succeeding treatment process (post-treatment process), the matter already subjected to plating treatment is washed in water, then washed in hot water and then dried. Much time is required for this succeeding treatment process and so productivity is low.
Moreover, the liquid waste discharged from plating factories is restricted in its quality by laws. Of all the discharged liquid waste produced as a result of plating operation, the cleaning liquid waste is, in general practice, added with a prescribed chemical(s) so as to become non-hazardous and thereafter, the heavy metal is removed in the form of a hydroxide by PH adjustment. And the discharged liquid waste having high concentration is processed by being added to the discharged cleaning liquid waste little by little. Or otherwise, such high concentration discharged liquid waste is separately treated and the treated water is mixed with a thin discharged cleaning liquid waste and then disposed.
However, the conventional discharged liquid waste treatment requires expensive equipment, various kinds of chemicals, a large amount of water and much time, and its productivity is very low.
As one attempt to solve those problems, the present applicant has developed a method of electrochemical reaction in which matter shifted into a supercritical state, an electrolytic solution and a surface active agent are introduced into a reaction vessel and emulsified. In that emulsified state, the electroplating is executed. After the plating treatment is executed, the supercritical matter is evaporated and discharged to the outside of the vessel. In doing so, the reaction vessel and the electrode, etc. can be cleaned without the need of a cleaning liquid. The present applicant has already filed a patent application with respect to the above method invention under Japanese Patent Application No. 2000-253572.
On the other hand, in the electroplating treatment, etc., a hydrogen gas and an oxygen gas are produced by electric decomposition of the electrolytic solution and bubbles thereof are stayed on the surface to be treated or moved thereon. As a result, plating omission and non-uniform plating occur. Moreover, since electric energy is consumed due to generation of the gases and the smooth plating treatment is jeopardized to that extent, the electric current efficiency is lowered.
As one attempt to solve this problem, Japanese Patent Application Non-Examined Publication No. 2000-226671, for example, discloses an electroless plating apparatus, in which a surface to be treated is placed in a hermetically closed-space with its face-up posture, the pressure in the space is then raised to a level equal to or higher than the atmospheric pressure, then this pressure is pulsated to dissolve the hydrogen gas bubbles produced with the progress of the reducing reaction at the time of electroless copper plating and accelerate the detachment of them from the surface to be treated.
In the electroless plating, however, hydrogen gas, etc. are necessarily generated with the progress of depositing reaction of plating and the method for suppressing the generation of gas is not practically usable because the suppression of the generation of gas adversely affects the deposition of plating, thus making it unable to execute the plating treatment itself.
That is to say, in the electroless plating treatment, the plating treatment is executed while allowing the generation of hydrogen gas, etc. and a proper stabilizer is applied to the vessel or nitrogen gas is used in order to cope with the unfavorable hydrogen gas.
Accordingly, it is practically impossible to employ the electroless plating treatment method which allows the generation of hydrogen gas, etc. to the electroplating treatment, etc.
Moreover, in the case where the electroplating treatment is executed through the above-mentioned method, an electrode must be disposed opposite to the surface to be treated. If the arrangement is made in this way, the hydrogen gas generated from the surface to be treated stays on the electrode. This prevents the smooth flow or passage of electric current through the electrolytic solution and makes it difficult to execute the electroplating treatment. Thus, the above method is unable to be applied to the electroplating treatment.
It is, therefore, a principal object of the present invention to provide a novel electrochemical reaction method and an electrochemical reaction apparatus thereof, which are high in reactability, in which electrochemical reaction can be executed efficiently, which is small or zero in amount of generation of liquid waste such as electrolytic solution and cleaning liquid and therefore, amicable to the environment, and in which it is no more required to clean the electrode, etc. with cleaning liquid after the reaction.
Another object of the present invention is to provide a method of electrochemical treatment such as electroplating, etc., and an electrochemical reaction apparatus thereof, which are suited to be used for electrochemical treatment such as, for example, electroplating, etc., and which are capable of executing various treatment processes safely, rationally and rapidly, using supercritical or subcritical matter.
A further object of the present invention is to provide a method of electrochemical treatment such as electroplating, etc., and an electrochemical reaction apparatus thereof, which are capable of processing the used-supercritical or subcritical matter such as carbon dioxide, treatment solution, etc. rationally and rapidly, which are capable of suppressing the amount of use of the acid picking solution, plating solution, etc. and reducing the amount of liquid waste generated from plating operation thereby preventing the pollution of the environment and achieving the improvement of the working environment, the enhancement of productivity and the reuse of the liquid waste.
A still further object of the present invention is to provide a method of electrochemical treatment such as electroplating, etc., and an electrochemical reaction apparatus thereof, which are capable of providing a beautiful finishing by remarkably improving the adhesion power of plating, and which are capable of easily realizing fine and uniform plating even at the reverse side and recessed-portion of the matter to be treated.
A yet further object of the present invention is to provide a method of electrochemical treatment such as electroplating, etc., and an electrochemical reaction apparatus thereof, which are capable of attaining elimination, miniaturization and light-weight of a vessel(s) required for each plating treatment thereby achieving reduction of the cost of equipment and compactness of the installation space.
An additional object of the present invention is to provide a method of electrochemical treatment such as electroplating, etc., and an electrochemical reaction apparatus thereof, which are suited to be used for electrochemical treatment such as, for example, electroplating, etc., and which are capable of executing electrochemical reaction rationally and efficiently by pressurizing the reaction vessel and suppressing electrolysis of a solvent in the electrolytic solution for the enhancement of electric current efficiency, thereby obtaining a fine and thin metallic film.
According to one aspect of the present invention, reaction is executed in a vessel containing matter shifted into a supercritical or subcritical state and an electrolytic solution. The expression xe2x80x9csupercritical statexe2x80x9d herein used refers to a state which is kept under a temperature/pressure higher than the critical point indicated in an entropy chart of temperature and pressure in a phase diagram. The matter shifted in this state is not in the form of gas nor liquid. According to this means, the reaction vessel is equalized in quality by the supercritical matter having a high diffusion constant and ion is efficiently supplied to the peripheral area of the electrode, etc., thereby enhancing the reactability. Moreover, since a small amount of electrolytic solution is good enough, the amount of liquid waste to be treated can be suppressed.
Moreover, by executing the reaction in a reaction vessel which contains therein supercritical matter, an electrolytic solution and a surface active agent and which is emulsified, the supercritical matter and the electrolytic solution are more uniformly dispersed and the reaction efficiency is enhanced at the surface of the electrode, etc.
The matter shifted into the supercritical state is at least one selected from the group of carbon dioxide, methane trifluoride, ethane, propane, butane, benzene, methylether and chloroform.
After the electrochemical reaction is executed, the matter in the supercritical state is shifted into a state equal to a critical point or lower. The supercritical matter is abruptly evaporated or liquefied by reducing pressure after the reaction. Accordingly, a flow is vigorously generated in the system so that impurities on the surface of the electrode, etc. are cleaned by being blown off.
In the electrochemical reaction method, the reaction in the reaction vessel is electroplating, electroforming, formation of an anodic oxide film, electrochemical polishing, electrochemical machining, electrophoretic coating, electrorefining, chemical conversion treatment, or electroless plating. Therefore, the industrial field to which the present invention is applicable can be specified.
That is to say, in the various industrial field of the above mentioned electroplating, etc., reaction is executed efficiently by storing supercritical matter, an electrolytic solution and a surface active agent, if necessary, in an electrolytic bath (or plating bath, treatment solution or the like).
Moreover, according to another aspect of the present invention, a reaction vessel containing an electrolytic matter and an electrolytic solution therein is shifted into a supercritical or subcritical state and in that state, the electrolytic matter is electrolyzed or the electrolyzed electrolytic matter and/or electrolytic matter contained in the electrolytic solution is deposited and adhered to the other electrode matter. Accordingly, the present invention is suited to be used for electrochemical treatment such as electroplating. For example, by using a carbon dioxide in a supercritical or subcritical state, the various treatment processes can be executed safely, rationally and rapidly. Moreover, the adhesion power of plating is remarkably improved, a beautiful finishing can be obtained, fine and uniform plating is realized even at the reverse side and recessed-portion of the matter to be treated and the productivity is enhanced. The treatment of the present invention can be applied to an electroforming method, an anodic oxide film formation method, and an electrochemical polishing method with the result of enhanced productivity and beautiful finishing.
Moreover, according to another aspect of the present invention, a reaction vessel containing an electrolytic matter therein is shifted into a supercritical or subcritical state, and in that state, the electrolytic matter is electrolyzed so as to be collected on the other electrode matter side. Accordingly, the present invention can be applied to a metal electrolytic extraction and refining method with the result of enhanced productivity and beautiful finishing.
Moreover, according to another aspect of the present invention, a reaction vessel containing an electrolytic matter therein is shifted into a supercritical or subcritical state- and in that state, the electrolytic matter is deposited and adhered to the matter to be treated. Accordingly, the present invention can be applied to an electroplating and chemical conversion treatment method without a need of a provision of an external electric field and with the result of enhanced productivity and beautiful finishing.
Moreover, according to another aspect of the present invention, after the electrolytic matter is electrolyzed or the electrolyzed electrode matter and/or the electrolytic matter contained in the electrolytic solution is deposited and adhered to the other electrode matter, or after the electrolytic matter is electrolyzed and the electrolyzed matter is collected at the other electrode matter side, the reaction vessel is shifted from the supercritical or subcritical state into the above-mentioned state equal to or lower than the critical point and then, the electrolytic solution and the supercritical or subcritical matter is brought back into a double-layer state and discharged. At the time of shifting, a vigorous flow is generated in the system of the reaction vessel, etc. so as to accelerate the cleaning and drying of the matter to be treated.
Moreover, according to another aspect of the present invention, after the electrode matter or electrolytic matter is electrolyzed, the matter in a supercritical or subcritical state is introduced into the reaction vessel and then the electrode matter is cleaned or the oxide film is removed therefrom. Accordingly, the various treatments are executed rationally and rapidly and the drying treatment is accelerated.
Moreover, according to another aspect of the present invention, after the electrode matter or electrolytic matter is electrolyzed, matter in a supercritical or subcritical state is introduced into the reaction vessel and the electrode matter or the electrolytic matter collected side is cleaned or dried. Accordingly, the various treatments are executed rationally and rapidly and the drying treatment is accelerated.
Moreover, according to another aspect of the present invention, at the time of electrolyzing the electrode matter, the supercritical or subcritical matter and the surface active agent are introduced into the reaction vessel and the inside of the reaction vessel is emulsified in the supercritical or subcritical state so that the electrode matter or the electrolyzed matter is deposited and adhered uniformly, rapidly and in high density. By doing so, for example, the adhesion power of plating is remarkably improved and a beautiful finishing can be obtained. Moreover, the plating treatment can be executed easily and uniformly even at the reverse side and the recessed part of the matter to be treated, and productivity is enhanced.
Moreover, according to another aspect of the present invention, a supercritical or subcritical matter, an oxide film removing solution and a surface active agent are introduced into the reaction vessel before an electrode matter or an electrolytic matter is electrolyzed, so that the reaction vessel is shifted into a supercritical or subcritical state. And in that state, the inside of the reaction vessel is emulsified. Accordingly, the various treatments are executed rationally, rapidly and in high density.
According to still another aspect of the present invention, reservoir vessels communicable with the reaction vessel are disposed at the outside of the reaction vessel, and the used-supercritical or subcritical matter, the electrolytic solution or cleaning or oxide film removed-matter is reserved in the reservoir vessels. Accordingly, the used-supercritical or subcritical matter, etc. are prevented from being discharged so that they can be reproduced and reused rationally and effectively.
Moreover, according to another aspect of the present invention, the used-supercritical or subcritical matter reserved in the reservoir vessels is reproduced and refluxed to the reaction vessel, or the used electrolytic solution or cleaning or oxide film removed-matter reserved in the reservoir vessels is reproduced and refluxed to the solution reservoir vessels. Accordingly, the used supercritical or subcritical matter and the used electrolytic matter, cleaning or oxide film removing matter or the like can be effectively utilized.
Moreover, according to another aspect of the present invention, a treatment process of deposition and adhesion of the electrode matter, and a preceding treatment process thereof, or an electrolyzing and collecting process of the electrolytic matter and a preceding treatment process thereof are executed in only one reaction vessel. Accordingly, the vessels required for each of the processes can be eliminated. Thus, the cost of the equipment can be lowered and the installation space can be made compact. Moreover, since the troublesome work for moving the matter to be treated for each vessel can be eliminated, the working efficiency is enhanced.
According to another aspect of the present invention, there are employed at least two reaction vessels capable of executing a treatment process of deposition and adhesion of the electrode, and preceding and succeeding treatment processes thereof, or an electrolyzing process of the electrolytic solution, and preceding and succeeding treatment processes thereof. The preceding and succeeding treatment processes are sequentially executed in these reaction vessels. Accordingly, electrochemical reaction of electroplating, etc. and various treatments related thereto can be executed rationally and a mass production thereof can be obtained.
Moreover, according to another aspect of the present invention, after a prescribed treatment process is executed in the reaction vessels, the electrolytic solution, cleaning or oxide film removing matter, or surface active agents in the reaction vessel on the side of the preceding treatment process can be moved into the reaction vessel on the side of the succeeding treatment process. Accordingly, the used solution can be utilized effectively and the cost of treatments can be reduced.
Moreover, according to another aspect of the present invention, after the electrode matter is electrolyzed or after the electrolyzed electrode matter is deposited and adhered to the other electrode matter, multilayer electrode matter is deposited and adhered to the other electrode matter using the reaction vessel. Accordingly, the preceding treatment and the treatment of deposition/adhesion of the electrode matter of the next layer can sequentially be executed without a need of carrying out the matter to be treated from the reaction vessel. Thus, workability and productivity can be enhanced.
According to still another aspect of the present invention, electrochemical reaction is executed by pressurizing the reaction vessel. Accordingly, the electrolysis of the solvent in the electrolytic solution caused by the electrochemical reaction can be suppressed, the generation of hydrogen gas can be suppressed and miniaturization of bubbles thereof and dissolving thereof into the electrolytic solution can be accelerated. Thus, a fine and thin metallic film can be obtained. Moreover, the electric current efficiency can be enhanced and the electrochemical reaction can be executed rationally and efficiently. In addition, since the electrochemical reaction can be realized in a state which is lower in temperature and in pressure than the supercritical state, the energy saving can be achieved to that extent, the equipment can be made small in size and light in weight and the operation cost can be reduced.
According to the present invention, a pressurized fluid is introduced into the reaction vessel so as to pressurize the reaction vessel. Accordingly, there can be obtained a safe and stable electrochemical reaction compared with the case where a pressurized gas is introduced.
Moreover, according to another aspect of the present invention, a surface active agent is applied to the reaction vessel and stirred, the pressurized solution and the electrolytic solution are emulsified to execute the electrochemical reaction and under pressure, a surface active agent is acted on the fine hydrogen gas and oxygen gas efficiently and rapidly. Accordingly, the gas can be peeled off the surface to be treated and dissolved in the electrolytic solution rapidly.
Moreover, according to another aspect of the present invention, before electrochemical reaction of the reaction vessel is executed, the pressurized liquid can be introduced into the reaction vessel and the used-pressurized liquid can be discharged from the reaction vessel. Accordingly, the reaction vessel, the electrodes and the surface to be treated can be cleaned and dried before and after the electrochemical reaction.
According to another aspect of the present invention, before electrochemical reaction of the reaction vessel is executed, the pressurized liquid is introduced into the reaction vessel so as to clean the electrode matter or remove the oxide film therefrom. Accordingly, the preceding treatment can be executed by the pressurized liquid and a stable electrochemical reaction can be realized.
Moreover, according to another aspect of the present invention, after the electrochemical reaction is executed in the reaction vessel, the pressurized liquid is introduced into the reaction vessel so as to clean or dry the electrode matter. Accordingly, the succeeding treatment can be executed by the pressurized liquid and the stability of the next electrochemical reaction can be obtained.
Moreover, according to another aspect of the present invention, reservoir vessels communicable with the reaction vessel are disposed at the outside of the reaction vessel, so that the used-supercritical or subcritical matter, the electrolytic solution or cleaning or oxide film removed-matter can be reserved in the reservoir vessels. Accordingly, the used-supercritical or subcritical matter, etc. can be prevented from being discharged outside and they can be reproduced and used rationally and effectively.
According to still another aspect of the present invention, the used-liquid reserved in the reservoir vessels is reproduced, so that the used-liquid can be refluxed to the reaction vessel, and the used-electrolytic solution or cleaning or oxide film removed-matter reserved in the reservoir vessels is reproduced so that the solution or matter can be refluxed to the solution reservoir vessels. Accordingly, the used pressurized liquid, cleaning liquid, oxygen film removed matter, etc. can be utilized effectively.
The above objects, features and advantages of the present invention will become more manifest from the following detailed description with reference to the accompanying drawings.